gwt3-processors

What is it ?

It's a set of helper processors that can speed up J2CL development by generating boiler-plate code.

The latest version: https://search.maven.org/search?q=g:org.treblereel.j2cl.processors

It contains the following features:

• @GWT3EntryPoint acts pretty much the same as Gwt2 EntryPoint, the annotated method will be called on application startup.

  public class App {
  
  @GWT3EntryPoint
  public void init() {
    HTMLButtonElement btn = (HTMLButtonElement) DomGlobal.document.createElement("button");
    btn.textContent = "PRESS ME !";
    }
  }

• @ES6Module allows us to use Es6 modules via JsInterop.

  @ES6Module
  @JsType(isNative = true, namespace = "org.treblereel.j2cl.shim")
  public class ES6Test {
    public String id;
    public native boolean isTest();
   }

   class ES6Test {
    constructor() {
      /** @type {string} */
      this.id = "#id"
    }
    /**
    * @return {boolean}
    */
    isTest() {
      return true;
    }
   }
  export { ES6Test };

• @GWT3Export allows a resulted JavaScript file to be called from the pure JavaScript environment.

  public class ExportTestClass {
  
      @GWT3Export
      public static String test(String s) {
        return s;
      }
    
      @GWT3Export
      public Promise<String> promise() {
        return Promise.resolve("Hello world!");
      }
  }

    var test = new org.treblereel.j2cl.exports.ExportTestClass();
  
    test.test('INSTANCE METHOD CALL');
  
    test.promise().then(function(result) {
       
    });

• @TranslationBundle j2cl-maven-plugin 0.21 brings us support of Closure's .xtb translation bundles that are a very effective way to translate your application.

  • Note: at the moment, .xtb support is only available for j2cl-maven-plugin 0.21 and above and works only in ADVANCED mode, otherwise default values will be used.

  To use @TranslationBundle, you need to do the following steps:

1. In the configuration section of j2cl-maven-plugin, enable .xtb auto discovery:

  <translationsFile>
    <auto>true</auto>
  </translationsFile>

2. To a set locale for current compilation, you need to add the following line to your pom.xml

  <defines>
    <goog.LOCALE>en</goog.LOCALE>
  </defines>

3. Create an interface MyBundle annotated with @TranslationBundle

  @TranslationBundle
  public interface MyBundle {
    ...
  }

The processor will generate the MyBundleImpl.java implementation in the same package where MyBundle is.

4. Create a translation property bundle for MyBundle with a locale declared in the following format:

   • MyBundle_en.properties or MyBundle_en_US.properties containing key value pairs like:
   • hello = Hello World! or hello = Hello {$arg}!
     
     Note: {$arg} is a placeholder for a string argument.

5. Declare corresponding methods in your MyBundle interface.

  @TranslationBundle
  public interface MyBundle {
  
    @TranslationKey(defaultValue = "Hello World!")
    String hello();
  
    @TranslationKey(defaultValue = "Hello {$arg}!")
    String hello(String arg);
  }

Default value is used if no translation property value is found for a given locale and key. If a value contains the {$arg} placeholder, it will be replaced with the argument provided to the method. Placeholder is surrounded with curly brackets and a corresponding method argument must be named the same;

6. Values can be in HTML, in this case HTML will be escaped. To unescape it, set unescapeHtmlEntities = true in the @TranslationKey annotation.

    @TranslationKey(defaultValue = "<div>HELLO</div>", unescapeHtmlEntities = true)
    String hello();

7. Each method should have a corresponding key value pair in a translation property file. Otherwise, a default value will be used. A method name can be overridden in @TranslationKey annotation.

    @TranslationKey(key = "greetings", defaultValue = "Hello World!")
    String hello();

• @GWT3Resource is a lightweight port of GWT2 resources. Its main purpose is to embed various resources into the JavaScript bundle.

  Here we declared a bundle of the resources that will be embedded into the JavaScript bundle:

      @GWT3Resource
      public interface CombinedClientBundle extends ClientBundle {
  
          @Source("logo.png")
          ImageResource linuxLogo();
  
          TextResource welcome();
  
          @DataResource.MimeType("audio/mpeg")
          @Source("alarmloop.mp3")
          DataResource resourceMimeTypeAnnotationAudioOgg();
     }

  Later, we can use it like this:

       CombinedClientBundle resources = CombinedClientBundleImpl.INSTANCE;
  
        DomGlobal.document.body.appendChild(resources.linuxLogo().getImage());
  
        HTMLDivElement container = (HTMLDivElement) DomGlobal.document.createElement("div");
        DomGlobal.document.body.appendChild(container);
        container.textContent = resources.welcome().getText();
  
        HTMLAudioElement audio = (HTMLAudioElement) DomGlobal.document.createElement("audio");
        DomGlobal.document.body.appendChild(audio);
        audio.src = resources.resourceMimeTypeAnnotationAudioOgg().asString();
        audio.controls = true;

Take a look at tests for more details.